<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>css var</title>
    <style>
        :root {
            --red: red;
        }
        .content {
            color: var(--red);
        }
    </style>
</head>
<body>
    <div class="content">xiaoshan.bug</div>
    <div class="content">hello world</div>
</body>
</html>